1. Technical Field
This invention relates to an electric water heater. More particularly, this invention relates to a compact electric water heater for domestic use that is pressureless, continuously self-cleaning, insulated, and energy efficient. The water heater preferably comprises insulation having multiple air spaces. The water heater also preferably includes one or more of an automatic fill switch, an inlet temperature sensor with a thermostat connected thereto, a high limit switch and a top nesting container for mounting an electric heating element. The high limit switch is preferably connected to a sensor plate. The sensor plate detects the temperature of the heat transfer liquid in the tank. By detecting the temperature of the heat transfer liquid in the tank as opposed to detecting the temperature of the water in the coil, a more accurate reading of the temperature of the heat transfer liquid in the tank is obtained.
2. Background Art
Conventional domestic electric water heaters include a steel tank, insulated by foam encased in a metal jacket. Cold water runs into the steel tank. The cold water is heated by lower and upper heating elements. Hot water exits through a pipe. While hot water is drained from the pipe, cold water mixes with the remaining hot water thus reducing the temperature of the remaining water.
In a conventional electric water heater, minerals typically settle out from the water to form sediments. Accumulation of sediments can eventually cause corrosion and leaks thereby reducing the heater""s efficiency. These inefficiencies lead to increased costs of heating. Furthermore, heat and occasionally excessive pressure of water entering the system from the cold-water source is generated in the tightly sealed tank. Property damage and personal injury can result from steam and water leaving the pressure relief valve or from explosion due to a failed valve.
Heating elements in conventional electric water heaters often fail before tank fail, and thus must be replaced more frequently than tanks. Replacement of the elements is a difficult task in conventional domestic electric water heaters and usually requires that the water supply be shut off and that the tank be drained prior to replacing the element.
Conventional electric water heaters have several safety drawbacks. They are typically constructed of a single layer of metal. The single layer of metal can be a hazardous condition when a person comes in contact with the unit or the metal due to repairs or through casual contact. Conventional electric water heating units may also have electrical wires positioned near the metal surface, which if contacted by a frayed or loose live wire, could cause electric shock and significant injury to an individual.
Another drawback of conventional water heater is that the many metal parts are prone to corrosion. The metal parts are also thermally conductive and are not ideal for insulating the heated water from ambient temperatures.
One object of the electric water heater of the present invention is to provide an efficient and inexpensive means for controlling the heating element within a hot water tank such that the temperature of the water is consistently kept at a desired temperature.
Another object of the present invention is to provide an electric water heater comprising: a tank having an inner wall and an outer wall wherein said inner wall and said outer wall are separated by a first open space region and said first open space region is filled at least partially with thermal insulation; further wherein said water tank is adapted to hold a quantity of non-pressurized and non-circulating heat transfer liquid; a top adapted to be separated from said tank, said top having an upper wall and lower wall wherein said upper wall and said lower wall are separated by a second open space region and said second open space region is filled at least partially with thermal insulation; at least one thermally conductive coil adapted to circulate water from a water inlet, said coil being mounted inside said tank and having said water inlet and a water outlet in communication with an exterior of said tank, further wherein said water inlet and said water outlet each extends outside of said water heater; at least one heating element attached to said top and positioned to extend downwardly through said top and heat said heat transfer liquid within said tank; a sensor plate in communication with said coil in a position proximate to said water inlet and wherein said sensor plate extends from said top to said coil; a thermostat connected to said sensor plate, wherein said thermostat is in thermal proximity with said sensor plate such that it activates said heating element when the temperature signaled by said sensor plate reaches a predetermined temperature; and wherein said heating element contacts and heats the heat transfer liquid inside the tank and said heat transfer liquid contacts said coil to heat water from a water supply that enters said water heater and circulates through said coil such that heated water leaves said water outlet.
It is another object of the present invention to provide an electric water heater comprising: a tank having an inner wall and an outer wall wherein said inner wall and said outer wall are separated by at least a single first open space region and said first open space region is filled at least in part with thermal insulation; further wherein said water tank is adapted to hold a quantity of non-pressurized and non-circulating heat transfer liquid; a top adapted to be separated from said tank, said top having an upper wall and lower wall wherein said upper wall and said lower wall are separated by at least a single second open space region and said second open space region is filled at least in part with thermal insulation; said top further having an opening that can receive a heating element mount adapted to extend downwardly inside and fluidly communicate with said heat transfer fluid, wherein said mount is sealing engaged in said opening and held in place by a gasket and a lip having a larger diameter than said opening, at least one thermally conductive coil adapted to circulate water from a water inlet said coil being mounted inside said tank and having said water inlet and a water outlet in communication with an exterior of said tank, further wherein said water inlet and said water outlet each extends outside of said water heater; at least one heating element mounted on said heating element mount and positioned to extend inside said heat transfer liquid within said tank; a sensor block in communication with said coil for receiving water from said coil and returning water to said coil; and a thermostat mounted on a side of said heating element mount and in thermal proximity to said sensor block such that it activates said heating element when water temperature signaled by said sensor block reaches a pre-determined temperature.